Method of forming dipped rubber shoes and last therefor



A nl A8, 1931. A. w. HOLMBERG ET AL 1,802,764

METHOD OF FORMING DIPPED RUBBER SHOES AND LAST THEREFOR Filed March 12, 1927 IN VEN 70Rs A Tram/5r Patented Apr. 28, 1931 UNITED STATES PATENT OFFICE ALBERT W. HOLMIBERG, OF SOUTH ORANGE, AND PARKE H. WATKINS, OF LEONIA,

NEW JERSEY, ASSIGNORS TO THE GOODYEARS INDIA RUBBER GLOVE MFG. COM- PANY, F NAUGATUCK, CONNECTICUT, A CORPORATION OF CONNECTICUT METHOD FORMING DIPPED RUBBER SHOES AND LAST THEREFOR Application filed March 12, 1927. Serial No. 174,744.

This invention relates to the manufacture of rubber shoes, more particularly it relates to a method and to an apparatus for manufacturing dipped rubber shoes.

In the manufacture of rubber footwear the article is ordinarily built up by superposition of previously out parts on a last, this operation requiring considerable skill and manual labor. The parts used by the operator are cut out from stock, considerable scrap being formed during the cutting operation, and further scrap is formed in trimming the parts after application to the last and in trimming the complete article. Some of this scrap,

where it is composed only of rubber composition, can be remilled, but scrap composed in part of rubber and part of fabric cannot be thus used and can only be ground up to form the so-called rag stock, or put through a reclaiming operation.

It is an object of this invention to provide a method of buildin a rubber shoe whereby labor and wastage of rubber composition are minimized. Another object is to provide a means for securing an insole or insole and foxing to a last while the remainder of the shoe is being constructed. A further object is to provide an improved means for accurately trimming the waste material from the assembled shoe. A further object is to provide an improved last for making rubber footwear, by coating with rubber in fluid form.

For a complete disclosure of the nature and objects of the invention, reference is had to the accompanying specification and drawings in which latter:

Fig. 1 is a side elevation of the last; Fig. 2 is a plan view ofthe last; Fig. 3 is a side elevation of a foothold; Fig. 4 is a transverse section along the line 44 of Fig. 1; and

Fig. 5 is a fragmentary view of the last showing a modification ofthe invention.

Referring to the drawings, the last upon which the foothold is built comprises a body portion 1 of the general shape ofthe front portion of a low shoe. Projecting rearwardly from the body portion is a strap portion 50 2 which projects a distance such that the length of the complete last approximates that of a shoe upon which the foothold is to be worn. The strap, portion 2 is of the same width as the strap of the foothold which is to be built thereon. Secured to the top and to the bottom of the strap portion of the last and protruding therefrom in effect outlining the strap of the foothold to be constructed, are two plates 3 and 4 which are secured to the last by means of screws 5. These plates are provided with -a sharp protruding rib or edge'6. While this edge has been illustrated as resembling a knife edge, an ordinary pro-,- jecting shoulder can be substituted therefor. The form is constructed of aluminum or of 5 any other suitable material. It is preferably given substantially the same shape on either side so that a foothold constructed thereon would be suitable for use on either a right or a left shoe but of course right and left lasts or forms might be used if desired.

Within the last there is provided a chamber 8 from which there extend pasages 9 through the bottom wall 10 and passages 11 through the side walls 12 of the last. A valve stem 13 is fastened into the upper part of the last and is connected with the chamber 8. The valve stem is designed to be connected to a source of suction which will 0 crate through the passageways 9 and 11 to 80 hold the usual insole or an insole and foxing in place. In the embodiment illustrated, the

insole edges are extended to form in effect a foxing, the edges being bent upward over the last so. that suction exerted through the passageways 11 will hold the same in place.

In the operation of manufacturing a dipped rubber foothold, an insole and foxing shown in dot and dash lines in Fig. 1 as 14 is prepared'out of paper, .cloth, or other suitable material. It is placed in proper position upon the last and the protruding portion is bent over the edges of the last. Suction is applied, thereby holding the combined foxing and insole in place. The last is now in condition to be subjected to a dipping operation in rubber composition whereby a deposit of the rubber composition is placed upon the last thereby forming the foothold. 10c

A suitable composition in which the last can Dry rubber (as latex containing approximately 30% solids) 100 Zinc diniethyl dithiocarbamate Carbon black Glue Sulphonated castor oil Trisodium phosphate Sulphur 52 Zinc oxide 1 This composition forms an approximately 35% dispersion of solids in water. The glue serves as a stabilizer; the sulphonated castor oil gives a smooth surface. to the deposited rubber composition; the trisodimn phosphate facilitates the cure and gives better aging qualities as well as helps to keep the latex in stable condition. It will be understood that the composition can be 'aried as desired without departing from the spirit of the invention. For example. other stabilizers may be substituted. such as casein, nekal which is a condensation product of an aromatic hydrocarbon and aliphatic alcohol in the presence of sulphuric acid, potassium oleate or alkalies. Other sulphonated vegetable oil can be substituted for the sulphonated castor oil. Softeners in suitable con dition can be added, such as spindle oil, mineral oils or in the form of emulsions; also drying and semidrying oils. Aniline dyes or pigments can be used for coloring the composition as desired. It is desirable that the latex composition shall be sufficiently thick so that runs will not develop when it applied to a surface and at the same time it should not be so thick that it will not run smoothly. It has been found that a dispersion containing approximately 50% solids is satisfactory. In such a dispersion the fillers are held suspended and the composition is sufficiently thick to prevent it from striking through the fabric. Also, with a dispersion of this thickness only a small num ber of dippings is necessary to form a deposit on the last of the desired thickness. The 35% dispersion as compounded can be evaporated to the desired thickness.

The last with the insole secured thereon is immersed in the dispersion, is removed therefrom and is held elevated for a short period of time to permit the excess composition to drain therefrom. The last is drained in a tilted position so that the composition drips away over the shoulder of the bottom plate 4, leaving a thin film of composition upon the last. The coated last is held over a mixture of rd alcohol and gfirds acetic acid to enable the vapors of the mixture to coagulate the surface of the film of composition. Alternatively, the composition can be coagulated by dipping the coated last in an approximately 50% acetic acid solution.

The last is dipped in the composition a second time, is removed therefrom and drained in an inverted position, the top plate 3 being at the bottom and the last tilted so that the composition drips from the shoulder 6 of the plate 3. Due to the presence of excess acetic acid from the step of coagulating the initial coating of rubber composition, the second film deposited is a relatively heavy coating. The composition deposited the second time is subjected to one of the coagulating steps just described.

The last is again dipped in rubber composition and is drained in the first mentioned position with the composition dripping from the shoulder of the bottom plate l. The third coating is of approximately the same thickness as the second. It is coagulated by dipping the last in a roughly 50% acetic acid solution after which it is washed with Water to remove the coagulent and is then dried. The purpose of draining the excess rubber composition from different shoulders of the last is to build up a bead adjacent each shoulder. By holding the last in a diagonal position with the plate 2 lowermost causing the composition to drain over the shoulder of the plate el, a thickened portion or bead of rubber composition accumulates adjacent the shoulderl ll-y draining the excess composition from the second dipping with the top plate lowermost and the dispersion dripping therefrom, a thickened portion is formed adjacent the shoulder formed by this plate. The deposit of dispersion resulting from the second dipping is relatively thick and a relatively thick bead is formed. By draining the dispersion from the third dipping over the shoulder of plate 2, the bead deposited by the first dipping and draining is greatly enlarged. Vhen a composition is used having the consistency of that described and when three clippings are made, a suitable height for the shoulder is approximately th of an inch. A bead 15 forms adjacent each shoulder having a thickness two or three times the thickness of the body of the shoe. The height of the shoulder will be varied with the composition and with the number of dippings. The purpose of forming a bead is to add strength to the strap of the foothold. The gauge of the foothold formed by the method described usually varies between .015 and .030 inches.

The last is now subjected to a trimming operation to sever the rubber composition which has coated the last beyond the knife edges. This can be accomplished conveniently by pressing a roller against the knife edge whereby the film of rubber composition is severed. Any suitable instrument, such as a knife, can be substituted for the roller.

The article after drying is then vulcanized and with the particular composition de scribed, this is accomplished by heating for approximately one hour at 220 F under suitable pressure if desired. It Will be understood that the conditions will vary with the composition used and any suitable method of vulcanization may be employed. If after washing the coagulated composition the deposit is not completely dried, curing should be done under pressure to avoid formation of blisters. The suction which was used to secure the insole to the last can be discontinued after sufficientcomposition is deposited to hold the same in place. After vulcanization, the completed foothold can easily be removed from the last.

A design can be formed upon the tread by passing a knurled roller over the surface of the same after the foothold has been built, but before vulcanization. Alternatively, the insole is embossed with the desired design and the layers of deposited composition will as sume the outlines of the design.

It may be desired to build a fabric upper into the foothold, in which case an upper 16 is formed of the desired shape which will constitute both an upper and insole such as is illustrated in Fig. 5. The upper is placed in position on the last and the dipping process is accomplished as previously described. The use of suction can be dispensed with when this type of upper is used. An advantage of having a fabric upper is that the surface which it presents to a shoe is comparatively frictionless. If the fabric upper is omitted from the foothold, the inner surface thereof can be halogenated, for example, treated with a solution of bromine, and will then present a frictionless surface to the shoe of the wearer.

l/Vhile the composition has been described as comprised of latex mixed with the compounding ingredients, any dispersion of rubber can be used, for example, vulcanized latex or an artificial dispersion. Also a solution of rubber containing compounding ingredients can'be substituted and some of the advantages of the invention retained. In case a solution of rubber is used, the steps of coagulating the composition will be omitted and the step of evaporating the solvent, will be added. By the method described, a foot hold has been obtained which is light in weight, inexpensive and flexible. The waste rubber resulting from the process of building a rubber shoe has been largely eliminated.

The edges of the foothold are trimmed away accurately at the outer edge of the bead thereby improving the appearance of the article and rendering all of the articles uniform.

It will be seen that by our invention footwear and other rubber articles can be formed with a minimum of manual labor and scrap loss, and that the articles can be made without the employment of skilled labor. While the invention is not to be so limited, it is particularly adaptable for the making of light Weight footwear, such as the foothold specifically shown and described.

Having thus described our invention, what we claim and desire to protect by Letters Patent is:

1. A form for making a dipped rubber article of footwear, comprising a body, and a rib carried by the body, said rib having a relatively sharp outer edge adapted to cooperate with a trimming implement to remove the waste material from the form after dipping and to thereby define an opening in the finished article.

2. A form for making dipped rubber footholds comprising a body, a narrow rearward projection thereon having a side contour approximately that of a foothold strap, and bead forming shoulders on the body and projection outlining the upper and lower openings of a finished foothold.

3. A form for making dipped rubber footwear comprising a body, means whereby footwear reinforcing elements may be pneumatically held in place during the building up of the article, and means for forming a head on the body disposed to outline a free edge of the finished article.

4. A last for footholds comprising a body portion, a strap portion, and shoulders carried by the body portion and strap portion positioned to bound the edges of a foothold to be formed upon the last.

5. The method of forming a dipped rubber shoe which comprises dipping in a fluid rubber composition a last having a shoulder bounding the outlines of at least a portion thereof, draining ofl the excess composition over the shoulder whereby athickened layer of rubber composition is formed adjoining the shoulder, evaporating the fluid from the composition, trimming along the shoulder, and vulcanizing.

6. The method of forming a dipped rubber shoe which comprises dipping in latex composition a last having a shoulder defining the outlines of a portion of an article to be built on the last, draining off the excess composition over the shoulder whereby a head of rubber composition is formed adjacent the shou'lder, coagulating the latex, trimming the excess rubber compositionalong the shoulder, and vulcanizing.

- 7, The method of forming a dipped rubber shoe which comprises securing a lining to a last by suction dipping the last in a fluid containing rubber composition, draining off the excess composition, and vulcanizing.

8. The method of forming a dipped rubber shoe which comprises embossing a suitable design on a lining, securing the lining to a last by suction, dipping the last and lining in a fluid containing rubber composition,

draining off the excess composition, and vulcanizing.

9. Process for manufacturing rubber footwear which consists in vacuously holding reinforcing elements of the article on a last, applying rubber in liquid form to the last and over the reinforcing elements, removing liquid from the rubber leaving a deposit of rubber over the last and reinforcing elements, and subsequently vulcanizing.

10. Process for manufacturing rubber footwear from aqueous dispersions of rubber which consists in vacuously holding fibrous reinforcing elements on a last, applying an aqueous dispersion of rubber to the last and reinforcing elements, drying the rubber deposit, and subsequently vulcanizing.

11. A process for manufacturing rubber footwear which consists in vacuously holding an insole and other reinforcing elements in place on a last, applying a rubber dispersion to the last and said elements simultaneously, coagulating the rubber on the last and repeating the application and coagulation of rubber thereon until the required thickness has been gained, and drying and vulcanizing.

12. A form for making an article of footwear, comprising a shoe last having a series of openings adjacent the sole portion only, means forevacuating said openings Whereby to hold reinforcing elements of a shoe sole against the last during dipping of the last in a coating composition to form a shoe, and one or more ribs carried by said last for defining the edges of openings in the finished shoe.

Signed at New York, New York, this 7th day of March, 1927.

ALBERT W. HOLMBERG. PARKE H. WATKINS. 

